This invention relates to a concealed latch for the doors of a trailer or cargo container and, in particular, to a substantially fully enclosed latch having a frangible handle and a shielded lock.
Cargo containers and truck trailers (herein referred to generically as trailers) are typically equipped with at least one pair of large, hinged doors having vertically sliding bars which engage holes or sockets in the floor and ceiling of the trailer to latch the doors in a closed position. The bars themselves are prevented from moving by a variety of locking devices such as pins, cams, or hasps.
Trailers are used for conveying goods or for temporary storage of goods, such as construction equipment at a job site. Theft is a difficult problem for owners or lessors of trailers, particularly trailers that are used for temporary storage of construction equipment, because the trailer is relatively exposed at night, especially if the trailer remains in the same location for several consecutive nights. Despite secure yards, fences, and locks on the doors of the trailers, thieves manage to overcome security devices and steal valuable goods and equipment. While the ban of chlorofluorocarbon based coolants has temporarily slowed thefts (the coolants were used to freeze the lock, which was then shattered with a hammer), brute force still succeeds in opening the doors of a trailer, e.g. by bending or breaking the exposed latching bars.
The problem of providing a secure latches and locks for trailers has been addressed in the prior art. For example, U.S. Pat. No. 4,742,701 (Scavetto) discloses a mechanism in which a concealed vertical bar has latching elements which pivot into or out of receptacles as the bar is raised or lowered. A lock, the shackle of which is manipulated from outside the trailer by way of a handle, is located in a recess in a door. U.S. Pat. No. 4,669,767 (Leto) discloses a trailer with rear doors having an exposed latch and a concealed bar inserted and locked in place from a side of the trailer. U.S. Pat. No. 2,452,521 (Johnson et al.) discloses an exposed door latch in which a pair of vertical bars are attached to a pivoting plate. A handle is also attached to the plate for rotating the plate and latching or unlatching the doors. In the latched position, a U-shaped metal loop attached to one of the bars extends through a slot in the handle for receiving the shackle of a lock.
Enclosed latches and locks of the prior art are complicated structures which are expensive to make and not particularly rugged or easy to use. Exposed latches and locks are subject to brute force attack in which the latching bars are bent. A lock on one side of a trailer and a latch on another side of the trailer are not convenient to use.
In view of the foregoing, it is therefore an object of the invention to provide an enclosed, mechanically simple, rugged latch for trailers.
Another object of the invention is to provide a concealed latch and lock for trailers in which the exposed portion of a handle for operating the latch breaks more easily than the rest of the latch and lock.
A further object of the invention is to provide a latch and lock for trailers in which only a handle for operating the latch is vulnerable to attack and the handle is frangible.